Thread monitor device for textile machinery

ABSTRACT

To check the presence of thread close to thread handling apparatus in which the thread is apt to balloon, two hook shaped metallic thread guides, together, form a thread guiding eye; the hook shaped guides are spaced from each other in the direction of thread travel, so that they are electrically insulated. The guides act, electrically, as separate electrodes and mechanically to, conjointly, form the guiding eye. The guide-electrodes are connected over high impedance input to a differential amplifier which responds to presence of or absence of the thread which, due to the ballooning tendency, alternately contacts the one and the other of the hook-shaped guide-electrodes, to transmit pulses due to electrostatic charge on the thread to the differential amplifier or, if the thread is conductive due to moisture and low resistance material, or the presence of metallic threads, connects, alternately, a source of potential to the differential amplifier. Absence of pulses is an indication of thread breakage. An integrator delays initial sensing to permit start-up.

United States Patent 1 Schwartz 1 THREAD MONITOR DEVICE FOR TEXTILEMACHINERY [75] Inventor: Hermann Schwartz, Pfaffikon, Switzerland [73]Assignee: Siegfried Peyer, Bach, Switzerland [22] Filed: Sept. 6, 1973[21] Appl. No.: 394,936

[30] Foreign Application Priority Data Oct. 11, 1972 Switzerland14843/72 [52] US. Cl 57/81, 57/34 R, ZOO/61.13, ZOO/61.18 [51] Int. ClD0lh 13/16 [58] Field of Search 57/78, 80, 81, 106, 34 R; ZOO/61.13,61.18; 242/157 R, 157 C [56] References Cited UNITED STATES PATENTS3,010,273 11/1961 Bailey 57/81 3,043,991 7/1962 Schneider et al.. 57/81X 3,114,233 12/1963 Guri 57/81 3,132,466 5/1964 Preisser 57/81 3,158,852ll/l964 Schacher 57/81 X 3,701,247 10/1972 Rehn et al. 57/81 3,772,52411/1973 Erbstein 57/81 X [451 Oct. 29, 1974 Primary Examiner.lohnPetrakes Attorney, Agent, or Firm-Flynn & Frishauf 57 ABSTRACT To checkthe presence of thread close to thread handling apparatus in which thethread is apt to balloon, two hook shaped metallic thread guides,together, form a thread guiding eye; the hook shaped guides are spacedfrom each other in the direction of thread travel, so that they areelectrically insulated. The guides act, electrically, as separateelectrodes and mechanically to, conjointly, form the guiding eye. Theguide-electrodes are connected over high impedance input to adifferential amplifier which responds to presence of or absence of thethread which, due to the ballooning tendency, alternately contacts theone and the other of the hook-shaped guide-electrodes, to transmitpulses due to electrostatic charge on the thread to the differentialamplifier or, if the thread is conductive due to moisture and lowresistance material, or the presence of metallic threads, connects,alternately, a source of potential to the differential amplifier.Absence of pulses is an indication of thread breakage. An integratordelays initial sensing to permit start-up.

10 Claims, 3 Drawing Figures PATENTEDumzs 1974 3.344.101

SHEEI 1 [IF 2 PATENTEDnm 29 I974 SHEET 2 0F 2 Hu k PDnCIDO JOMFZOU Thepresent invention relates to a thread monitoring and detection device,and particularly such a device which is adapted to cooperate with threadhandling apparatus in which the thread balloons outwardly, when thedevice is in operation.

Various types of textile machinery require accurate monitoring of thepresence of threads, and apparatus which, upon absence of thread,provide an alarm signal. Such thread monitor devices utilize variousmechanical, electrical, and electronic and systems. Some electronicsystems check axial, or radial movement of the thread and obtain asignal for the presence, or absence of the thread.

In many instances it is possible to locate the thread sensing device ina region where the thread is longitudinally guided, that is, where ithas relatively small radial movement. In some textile machinery,however, such as spooling machines, and spinning machines, and threadwinding machines, reliable thread sensing is only obtained if the threadis sensed after all machine elements have been passed thereby, that is,if the presence or absence of thread is sensed preferably immediately inadvance of it being wound on the spool. The sensing element must then belocated in the free space between the operating elements of the machineand the subsequent winding device. In this region, however, the

thread is free and not guided. Such apparatus, often,

utilizes a spooling arrangement in which the thread balloons radiallyoutwardly due to centrifugal force, and is subjected to circular motion,the size of which depends on the winding speed and the spool diameter atany time. This circular motion is commonly referred to as ballooning.

Various physical arrangements have been proposed to electronicallycontrol the presence or absence of a thread at this stage. Someapparatus utilize photoelectric, capacitative or piezoelectric systems.The static charge on the thread can also be detected. For static chargedetection, the thread is either electrically charged, by application ofan electric charge thereto, or the thread is subjected to friction whichcauses an electric charge build-up. The surface of the thread, however,has only low capacity and a certain time is required for the thread topass from the charge point to the sensing device. The thread, as aremoving charge carrier therefore must have an extremely high electricalresistance if the charge is to be maintained for any period of time.Textile threads of natural fibers require, however, a relatively highdegree of moisture for machine handling; synthetic threads frequentlyare treated with chemicals which prevent acceptance of static chargesduring production of the thread. Electrical resistance of the thread issubstantially reduced in these systems, so that electrostatic chargecannot be ensured. Textile threads which are mixed with metallic fiberscannot be used as charge carriers for static charges at all. Thus, knownthread sensing or monitoring devices can be used only selectively.

It is an object of the present invention to provide a thread sensingelement which permits sensing of a running thread independent of itsphysical characteristics, and within the region where the thread is aptto balloon.

Subject matter of the present invention Briefly, two hook-shaped threadguides are located, spaced from each other, in the thread runningdirection, such that, together, in projection they form a thread eyewith their free ends. The hook-shaped guide elements are metallic, andare connected over resistors with a source of direct current in order toprovide a voltage drop between the two elements, if connected by ametallic thread; they are coupled over capacitors with an input, each,of a differential amplifier in order to provide an output signaldepending on the presence of thread and motion of the thread within theeye formed by the two guides. The guides thus act, to define the threadeye and electrically as separate electrodes, and may be termedguide-electrodes.

The invention will be described by way of example with reference to theaccompanying drawings, wherein:

FIG. 1 is a top view of the thread guiding eye formed by the twoelements;

FIG. 2 is a front view of the elements, highly schematic, andillustrating the position of a thread applied to a spooling device; and

FIG. 3 is a circuit diagram of the arrangement in accordance with thepresent invention.

The thread sensing device, see FIGS. 1 and 2, includes two similarhook-shaped metal elements 1' and 1". They are made, preferably, ofsteel wire about 3 to 4 mm diameter, and coated with a hard chromefinish. Each end of the thread guide is bent over hook-shaped, and thetwo hook-shaped guide elements are located to be offset with respect toeach other by so that they, together, form, in projection, a threadguiding eye 2. The hook-shaped elements are spaced from each other byabout 2 3 mm, in the direction of thread movement. This permits easythreading of a thread F (FIG. 2) and further separates the hook-shapedelements electrically from each other. The thread guide eye, that is,the two elements, are located so that they are placed in the balloonformed by the thread when it is wound on a spool 8 (see FIG. 2), in sucha manner that, as the thread forms its circular rotation, it isconstantly in contact with the limiting surfaces defining the eye 2.Thus, the thread alternately contacts the one or the other element 1' or1'', respectively; upon transition from one to the other, both elementsmay be contacted together. These different contact zones of the threads,with the respective elements, are essential for the operation of thesystem, as will be described below. FIG. 2 illustrates, in solid line,the thread when wound on the left side of the spool 8, at which point itcontacts only thread guide element 1", and in chain dotted line theposition of the thread when the spool has revolved 180, and the threadcontacts the element 1'.

The thread guide element 1" is connected over a high resistance resistorR1 with the positive terminal of a voltage source (FIG. 3), for example+24V; the other element 1 is connected to the negative terminal of thesource over a resistor R2. A voltage, therefore, of 24 volts is appliedbetween the two elements 1', 1". The two guide elements form electrodes,which are connected over coupling capacitors C1, C2 to two highresistance inputs of a differential amplifier 3. The resistors R1, R2must be high resistors, and resistances of about 10 megohms aresuitable. The output of the differential amplifier 3 is connected to anintegrator 4 which, in turn, is connected to a trigger circuit 5, theoutput of which is connected to an alarm 6 and to a monostablemultivibrator 7, to initiate further control functions.

The differential amplifier will accept surrounding noise voltages due tothe high input impedance, which are applied by capacitative or inductivecoupling to the elements 1', 1". These noise voltages are primarily atpower supply frequency, and are derived from usual power supply cables,for drive motors, supplies for supervisory equipment and the like. Adifferential amplifier having an input sensitivity of 50 millivoltswould be rapidly blocked by'noise frequencies, particularly since therotational frequency of thread balloons, from experience, falls in theregion of 50 200 Hz, that is, within the range of power line frequenciesand the third harmonic thereof. Thus, filters cannot be used. If boththread guides are exactly equal, and have the same input capacitance tothe differential amplifier, then noise signals will be induced in bothhook-shaped elements with equal amplitude and phase, which will betransmitted with equal amplitude and phase to the differential amplifierso that it willnot provide an output signal.

Let it be assumed that the thread is of high resistance, and thuscapable of holding a static charge, at least for a short period of time.It is not necessary to provide a specific static charge tothe.thread-,,or to utilize any auxiliary charging devices. If the threadhas received any charge, for example due to friction with some elementof machinery, then this static charge is alternately applied to thehook-shaped elements 1 and 1" respectively, and transmitted to therespective amplifier inputs in the form of pulses. If the thread has notreceived any charge as yet, then friction with the hook-shaped elements,which are, respectively, connected to positive and negative terminals ofthe supply, will apply an electrostatic charge thereto, which chargewill be alternately exchanged between the guide elements 1', 1" thuslikewise providing pulse type signals to the amplifier 3.

Let it be assumed that, under other conditions, a thread is used whichhas low electrical resistance, for example due to moisture, applicationof chemicals, or the like, or that the thread-includes metallicfilaments or fibers,so that its resistance is 0. Under those conditionsno static charge can be transferred. The thread, however, contacts thetwo elements 1, 1, alternately, as it forms the thread balloon. For eachrotation within the balloon, the thread touches both elements 1, 1"simultaneously, although only instantaneously; for each rotation of thethread, therefore, the electrical resistance of the thread is twiceplaced over the thread guides l, 1" between the resistors R1 and R2.This leads to a change of voltage at the two resistors'Capacitor C1 thentransmits negative pulses, and capacitor C2 transmits positive pulses toamplifier 3. Assuming input impedance and sensitivity as above given, athread resistance of 10,000 Megohms per centimeter of thread wouldalready provide a sufficient signal to the amplifier.

'Thesystem,"therefore, utilizes a signal which is obtained byelectrostatic charge on the thread, or by thread resistance, and it isindependent of the material, or of its electrical characteristics.

The output signal from differential amplifier 3 is rectified in arectifier (not shown) and applied to an integrator '4. integrator 4integrates for a short period of time, for example for about 2 seconds,if a signal is present. Then a pulse is applied to set the triggercircuit 5, which may be an ordinary flip-flop. The delay preventsgeneration of a control signal upon threading of the thread or due tomomentary manual contact with the thread guides. lf a thread signal ispresent for two seconds, then the circuit 5 changes state, and thesystem is in monitor or thread sensing condition. If the thread ismissing, or if there is no thread motion, then the flip-flop 5automatically switches back, immediately, which provides an alarm on alamp 6, for example, and additionally a trigger pulse to a monostablemultivibrator 7, which provides an output control pulse to controlfurther alarm apparatus, or which is available as a trigger pulse forother control functions.

The flip-flop 5, thus, is a l-input flip-flop which is held its setposition by a signal from integrator 4 that changes to reset immediatelyupon cessation of this signal. The time delay of the combined circuits4, 5, thus is unilateral.

Various changes and modifications may be made within the scope of theinventive concept.

The guide elements 1, 1" may be insulated at their facing surfaces andthen actually brought in contact with each other, so long as they areelectrically insulated by high quality insulation without leakage pathswhich might detract from sensing of the thread. The separation of theseelements, then, will be that determined by the thickness of theseparating, insulating layer.

1 claim: 1. Thread monitor-device, particularly for thread handlingapparatus in which the thread forms a ballon comprising two hook-shapedthread guides (1', 1") of electrically conductive material, having theirhooks located to be spaced from each other, in the direction of threadtravel electrically insulated from each other to form, electrically twoelectrodes, said guides forming mechanically, in the projection ofthread travel, a thread guide eye (2);

a source of electrical energy (V);

high impedance means R1, R2) connecting the respective threadguide-electrodes (1', 1") to said source;

a differential amplifier (3);

and means (C1, C2) coupling the thread guideelectrodes 1, 1") to arespective input, each, of the differential amplifier, said differentialamplifier providing an output signal representative of motion of threadthrough the thread guide eye (2) formed by said thread guide-electrodes1', 1").

2. Device according to claim 1 wherein the coupling means comprisescoupling capacitors C1, C2).

3. Device according to claim 1 wherein the thread guide-electrodes 1',1") have approximately bent-over ends and are offset by about 180 withrespect to each other.

4. Device according to claim 1 wherein the thread guides (1', 1"), each,are made of steel wire with a hardened surface.

5. Device according to claim 1 wherein the thread guides (1', l") aremade of steel wire with a hard chrome surface.

6. Device according to claim 1 further comprising an integrator (4)connected to the differential amplifier and a bistable flip-flop (5)connected to the integrator and changing state when the integratorintegrates an output signal from the differential amplifier in adirection representative of presence of a signal.

7. Device according to claim 6 wherein the integrator (4) and themonostable flip-flop 5) provide a unidirectional delay of the outputsignal from the differentiator, the flip-flop responding immediatelyupon change of direction of output from the differential amplifier.

8. Device according to claim 6 further comprising a monostablemultivibrator triggered by change of state of said flip-flop andproviding an output control pulse.

9. Device according to claim 1 wherein said thread guide-electrodes (1',1") are similar, and spaced from each other in the direction of travelof the thread by a distance sufficient to electrically insulate saidguideelectrodes (1, 1) from each other, in the absence of a conductivethread, but insufficient to cause changes in phase or amplitude of straynoise signals induced therein.

10. Device according to claim 1 wherein the thread guides (1', 1") aresteel wires with a hardened surface of approximately 3 to 4 mm diameter,and are spaced from each other, in the direction of thread travel, by adistance which is sufficient to provide electrical insulation betweensaid guide-electrodes l, l"), in the absence of a thread, and not morethan about the diameter of the wires forming said thread guides 1, 1").

1. Thread monitor-device, particularly for thread handling apparatus inwhich the thread forms a ballon comprising two hook-shaped thread guides(1'', 1'''') of electrically conductive material, having their hookslocated to be spaced from each other, in the direction of thread travelelectrically insulated from each other to form, electrically twoelectrodes, said guides forming mechanically, in the projection ofthread travel, a thread guide eye (2); a source of electrical energy(V); high impedance means (R1, R2) connecting the respective threadguide-electrodes (1'', 1'''') to said source; a differential amplifier(3); and means (C1, C2) coupling the thread guide-electrodes (1'',1'''') to a respective input, each, of the differential amplifier, saiddifferential amplifier providing an output signal representative ofmotion of thread through the thread guide eye (2) formed by said threadguide-electrodes (1'', 1'''').
 2. Device according to claim 1 whereinthe coupling means comprises coupling capacitors (C1, C2).
 3. Deviceaccording to claim 1 wherein the thread guide-electrodes (1'', 1'''')have approximately 180* bent-over ends and are offset by about 180* withrespect to each other.
 4. Device according to claim 1 wherein the threadguides (1'', 1''''), each, are made of steel wire with a hardenedsurface.
 5. Device according to claim 1 wherein the thread guides (1'',1'''') are made of steel wire with a hard chrome surface.
 6. Deviceaccording to claim 1 further comprising an integrator (4) connected tothe differential amplifier (3); and a bistable flip-flop (5) connectedto the integrator and changing state when the integrator integrates anoutput signal from the differential amplifier in a directionrepresentative of presence of a signal.
 7. Device according to claim 6wherein the integrator (4) and the monostable flip-flop (5) provide aunidirectional delay of the output signal from the differentiator, theflip-flop responding immediately upon change of direction of output fromthe differential amplifier.
 8. Device according to claim 6 furthercomprising a monostable multivibrator triggered by change of state ofsaid flip-flop and providing an oUtput control pulse.
 9. Deviceaccording to claim 1 wherein said thread guide-electrodes (1'', 1'''')are similar, and spaced from each other in the direction of travel ofthe thread by a distance sufficient to electrically insulate saidguide-electrodes (1'', 1'''') from each other, in the absence of aconductive thread, but insufficient to cause changes in phase oramplitude of stray noise signals induced therein.
 10. Device accordingto claim 1 wherein the thread guides (1'', 1'''') are steel wires with ahardened surface of approximately 3 to 4 mm diameter, and are spacedfrom each other, in the direction of thread travel, by a distance whichis sufficient to provide electrical insulation between saidguide-electrodes (1'', 1''''), in the absence of a thread, and not morethan about the diameter of the wires forming said thread guides (1'',1'''').